Field
The disclosure relates to antennas for wireless communications devices.
Background
State-of-the-art wireless communications devices such as smart phones often require broadband antennas to accommodate multiple frequency bands, e.g., as dictated by the long-term evolution (LTE) system and other existing wireless wide area network (WWAN) mobile networks. For example, current fourth generation (4G) LTE smart phones are typically required to support a plurality of frequency bands, including LTE 700 (698-787 MHz), GSM 850 (824-894 MHz), GSM 900 (880-960 MHz), etc., in addition to other bands such as the global positioning system (GPS) band (1.575 GHz). In some implementations, a wireless device may be required to process radio signals over as many as eight or nine frequency bands, or more.
To support such multiple frequency bands, wireless devices may employ antennas operating over two or more broad bands that collectively cover the above-mentioned frequency bands, e.g., a low broad band spanning 700 MHz-960 MHz and a high broad band spanning 1710 MHz-2690 MHz. Per techniques of antenna design, a small antenna size usually corresponds to narrow bandwidth and low radiation efficiency. Accordingly, to accommodate such a broad bandwidth, each antenna requires a minimum volume or clearance, which mandates a minimum size for the design. In another aspect of modern wireless devices, multiple antennas are required to implement a feature known as multiple-input multiple-output (MIMO) to enhance wireless channel capacity.
To accommodate the aforementioned features, a wireless device may typically be required to include two or more antennas. However, due to the continuing trends toward reduction of phone size, optimization of industry design (ID), and the increase of function, very limited internal space within the wireless device is left for the antennas. These considerations complicate the design of LTE/MIMO antennas for wireless devices, as antennas must be provided in a restricted small space while nevertheless exhibiting sufficiently large bandwidth and radiation performance.
It would thus be desirable to provide techniques for design multiple antennas for a wireless device having sufficient bandwidth and performance with relatively small physical dimensions.